This means that the codebase for OpenBSD 5.1 is being identified. Snapshots of -current downloaded now will be very close to what will officially be released as OpenBSD 5.1 in May since time needs to be allotted for CD manufacture.

True supporters of the OpenBSD project will order official CD sets even if they download ISO's from the mirrors. Remember, the project is predominantly self-funded from the sales of official CD sets, t-shirts, etc. Announcement of availability will be found on the project's Website in the next few weeks.

Work on threading has been seen in the check-in's most of the 5.1 development cycle. This tends to be typical of the project's development style -- incrementally work on features & roll them out as they are deemed stable by the developers. Given the complexity & ramifications of threading, seeing that this feature is still being baked in the background is not surprising at all.